Abstract: Multidisciplinary scholars have argued the importance of nature in human health for the past several decades (Kellert & Wilson, 1993; Roszak, 1992), and numerous researchers have identified the positive effects of nature on human wellness (Brymer, Cuddihy, & Sharma-Brymer, 2010; Kuo, 2010). The profession of counseling is based on the philosophy of human wellness (Myers, 1992), although the current multidisciplinary wellness models (Myers & Sweeney, 2008) seem to overlook the wellness benefits of nature. As a way to begin the systematic exploration of nature in professional counseling, Reese and Myers (2012) developed the construct of EcoWellness and described the construct as the missing link in holistic wellness models in counseling. They recommended that the next step in exploring the construct included the development of an instrument operationalizing EcoWellness and its underlying constructs. Thus, the purpose of this study was to develop and assess the initial validity and reliability of the Reese EcoWellness Inventory (REI). The researcher utilized a six-step instrument development method that included the pilot testing of an initial 111-item instrument with a convenience sample of college students (N = 264). After modification of the REI, a revised 62-item instrument was tested and evaluated with a simple random sample recruited from Researchmatch.org (N = 853). Participants completed the REI, the Five-Factor Wellness Inventory (Myers & Sweeney, 2005b), and the Marlowe-Crowne Social Desirability Scale Short Form (Strahan & Gerbasi, 1972) in testing the initial validity and reliability of the REI. Results of confirmatory and exploratory factor analyses and the associated univariate tests demonstrated a mixed picture of the instrument's validity and reliability. A lower-level factor model was tested and it was found to possess adequate model fit. It was determined that the second-order factor of EcoWellness dictated the relationships between the lower-level factors. The development and testing of the REI provides an initial empirical foundation for the integration of nature into professional counseling and counselor education. Further research is needed to replicate and extend the study findings through utilizing samples more inclusive of national distributions of demographic characteristics such as age, gender, and ethnicity.